I'm not saying no way to a Listed unit. My question is, IS it a Listed unit?.
"This construction does comply with NFPA-20, UL-218 and FM-1321/1323"
I'm always suspicious (even of myself!). "Does comply" could be weasel-wording for "we designed it to meet the requirements of the standard. It was never submitted to an NRTL for certification, but in our opinion it does comply".
I've seen this a gazillion times in telecom. NEBS testing, to meet baby bell's network safety and reliability testing, cost around $100,000 for a complete set of tests on a typical product. Consequently, in marketing literature the words "meets NEBS requirement" and "designed for NEBS" are more common than "NEBS certified". Why spend a hundred grand when you can just use a misleading phrase instead?